System architecture, structure and method for hybrid random access memory in a system-on-chip

ABSTRACT

A hybrid random access memory for a system-on-chip (SOC), including a semiconductor substrate with a MRAM region and a ReRAM region, a first dielectric layer on the semiconductor substrate, multiple ReRAM cells in the first dielectric layer on the ReRAM region, a second dielectric layer above the first dielectric layer, and multiple MRAM cells in the second dielectric layer on the MRAM region.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates generally to a system architecture forhybrid random access memory, and more specifically, to a systemarchitecture for hybrid random access memory with magnetoresistiverandom access memory (MRAM) and resistive random access memory (ReRAM)in a system-on-chip.

2. Description of the Prior Art

After years of research and development, there are several emergingmemories rising the in electronic industry, such as 3D XPoint,magnetoresistive random access memory (MRAM), phase change memory (PCM),resistive random access memory (ReRAM) and ferroelectric random accessmemory (FeRAM). Some of these emerging memories are even expected toreplace dynamic random access memory (DRAM), NOR flash, NAND flash andstatic random access memory (SRAM) widely used in current electronicproducts, and start to be used in standalone chip and applicationspecific integrated circuit (ASIC), microcontroller or even processor,to make them more competitive than conventional memory technologies.

With respect to current microcontroller architecture and AI application,the memory required should meet the needs of high performance andnon-volatility, thus the emerging memories with these characteristicsare good options. However, the application of these emerging memories isonly at system level. Hybrid emerging memories integrated andmanufactured in a system-on-chip (SOC) is still not achievable.Therefore, those persons skilled in the art still need to furtherresearch and improve current hybrid random access memory architecture.

SUMMARY OF THE INVENTION

In light of the fact that memory system architecture nowadays andrelevant process still can't integrate and achieve hybrid memoryoperation in a system-on-chip (SOC), the present invention herebyprovides a system architecture, structure and manufacturing method forhybrid random access memory integrated with magnetoresistive randomaccess memory (MRAM) and resistive random-access memory (ReRAM) in asystem-on-chip. This system architecture with hybrid random accessmemory is suitable for high-performance microcontroller and AIapplication, and can meet the needs of high-speed/low-speed access anddigital/analog circuit.

One aspect of the present invention is to provide a system architecturefor hybrid random access memory in a system-on-chip, including acomputing unit, a hybrid register coupled to the computing unit,multiple magnetoresistive random access memory (MRAM) blocks, whereineach of the MRAM blocks comprises multiple MRAM cells coupled to a MRAMcontroller, and the MRAM controller is coupled to the hybrid register,and multiple resistive random-access memory (ReRAM) blocks, wherein eachof the ReRAM blocks comprises multiple ReRAM cells coupled to a ReRAMcontroller, and the ReRAM controller is coupled to the hybrid register,wherein the ReRAM cells and the MRAM cells are on the same semiconductorsubstrate.

Another aspect of the present invention is to provide a hybrid randomaccess memory in a system-on-chip, including a semiconductor substratewith a MRAM region and a ReRAM region, a first dielectric layer on thesemiconductor substrate, multiple ReRAM cells in the first dielectriclayer on the ReRAM region, a second dielectric layer above the firstdielectric layer, and multiple MRAM cells in the second dielectric layeron the MRAM region.

Still another aspect of the present invention is to provide a method ofmanufacturing a hybrid random access memory in a system-on-chip,including steps of providing a semiconductor substrate with a MRAMregion and a ReRAM region, forming multiple ReRAM cells in the ReRAMregion on the semiconductor substrate, forming a first dielectric layeron the semiconductor substrate, wherein the ReRAM cells are in the firstdielectric layer, forming multiple MRAM cells in the MRAM region on thefirst dielectric layer, and forming a second dielectric layer on thefirst dielectric layer, wherein the MRAM cells are in the seconddielectric layer.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the embodiments, and are incorporated in and constituteapart of this specification. The drawings illustrate some of theembodiments and, together with the description, serve to explain theirprinciples. In the drawings:

FIG. 1 is a system architecture diagram of a hybrid random access memoryin accordance with the embodiment of present invention;

FIG. 2 is a fundamental system architecture diagram of a hybrid randomaccess memory in accordance with the embodiment of present invention;and

FIGS. 3-14 are cross-sections of a process flow of manufacturing twodifferent memories, i.e. MRAM and ReRAM, on the same wafer.

It should be noted that all the figures are diagrammatic. Relativedimensions and proportions of parts of the drawings have been shownexaggerated or reduced in size, for the sake of clarity and conveniencein the drawings. The same reference signs are generally used to refer tocorresponding or similar features in modified and different embodiments.

DETAILED DESCRIPTION

Reference now be made in detail to exemplary embodiments of theinvention, which are illustrated in the accompanying drawings in orderto understand and implement the present disclosure and to realize thetechnical effect. It can be understood that the following descriptionhas been made only by way of example, but not to limit the presentdisclosure. Various embodiments of the present disclosure and variousfeatures in the embodiments that are not conflicted with each other canbe combined and rearranged in various ways. Without departing from thespirit and scope of the present disclosure, modifications, equivalents,or improvements to the present disclosure are understandable to thoseskilled in the art and are intended to be encompassed within the scopeof the present disclosure.

It should be readily understood that the meaning of “on,” “above,” and“over” in the present disclosure should be interpreted in the broadestmanner such that “on” not only means “directly on” something but alsoincludes the meaning of “on” something with an intermediate feature or alayer therebetween, and that “above” or “over” not only means themeaning of “above” or “over” something but can also include the meaningit is “above” or “over” something with no intermediate feature or layertherebetween (i.e., directly on something).

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper,” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures.

In general, terminology may be understood at least in part from usage incontext. For example, the term “one or more” as used herein, dependingat least in part upon context, may be used to describe any feature,structure, or characteristic in a singular sense or may be used todescribe combinations of features, structures or characteristics in aplural sense. Similarly, terms, such as “a,” “an,” or “the,” again, maybe understood to convey a singular usage or to convey a plural usage,depending at least in part upon context. In addition, the term “basedon” may be understood as not necessarily intended to convey an exclusiveset of factors and may, instead, allow for existence of additionalfactors not necessarily expressly described, again, depending at leastin part on context.

It should be further understood that the terms “comprises” and/or“comprising”, when used in this specification, specify the presence ofstated features, integers, steps, operations, elements, and/orcomponents, but do not preclude the presence or addition of one or moreother features, integers, steps, operations, elements, components,and/or groups thereof.

As used herein, the term “substrate” refers to a material onto whichsubsequent material layers are added. The substrate itself can bepatterned. Materials added on top of the substrate can be patterned orcan remain non-patterned. Furthermore, the substrate can include a widearray of semiconductor materials, such as silicon, germanium, galliumarsenide, indium phosphide, etc. Alternatively, the substrate can bemade from an electrically non-conductive material, such as a glass, aplastic, or a sapphire wafer.

As used herein, the term “layer” refers to a material portion includinga region with a thickness. A layer can extend over the entirety of anunderlying or overlying structure, or may have an extent less than theextent of an underlying or overlying structure. Further, a layer can bea region of a homogeneous or inhomogeneous continuous structure that hasa thickness less than the thickness of the continuous structure. Forexample, a layer can be located between any pair of horizontal planesbetween, or at, a top surface and a bottom surface of the continuousstructure. A layer can extend horizontally, vertically, and/or along atapered surface. A substrate can be a layer, can include one or morelayers therein, and/or can have one or more layer thereupon, thereabove,and/or therebelow. A layer can include multiple layers. For example, aninterconnect layer can include one or more conductor and contact layers(in which contacts, interconnect lines, and/or through holes are formed)and one or more dielectric layers.

Furthermore, as used herein, RAID is an abbreviation of redundant arrayof independent disks. In general, RAID technology is a method of storingdata on multiple disks or memories. By storing data on different disksor memories, I/O operation may be overlapped in a balancing fashion toimprove system performance. Since multiple disks or memories mayincrease mean time between failures (MTBF), storing data in RAID mayimprove failure tolerance.

The present invention provides a system architecture for hybrid randomaccess memory with different magnetoresistive random access memory(MRAM) and resistive random-access memory (ReRAM). More particularly,the different MRAM and ReRAM are made in the same process and on thesame wafer or substrate, with the benefit of process integration andapplicability in system-on-chip (SOC) design.

Please refer now to FIG. 1 , which is a system architecture diagram ofhybrid random access memory in accordance with the embodiment of presentinvention. It should be noted that this architecture implements datastorage including two different memories, i.e. MRAM and ReRAM.Generally, MRAM is a non-volatile memory whose data is stored bymagnetic storage devices rather than been stored in electric charge orcurrent form. ReRAM is also a kind of non-volatile memory, with anoperating principle that resistance of transition metal oxides in thememory cell would change along with the bias applied thereon torepresent the stored values of a bit.

As shown in figure, the system architecture 100 may be applied inmicrocontroller (MCU) or in system-on-chip (SOC). A hybrid register 120is included inside and is coupled to a computing unit 110. A data backupunit 102, a MRAM RAID controller/decoder 104 and a ReRAM RAIDcontroller/decoder 108 are coupled to the hybrid register 120. A databackup unit 106 and a MRAM block 130 are coupled to the MRAM RAIDcontroller 104. MRAM RAID controller 104 and ReRAM RAID controller maymanage the data access respectively in MRAM block 130 and ReRAM block140 in physical model and logical model.

As shown in the figure, each MRAM block 130 includes multiple MRAM cells131, a hot spare 132 coupled to the MRAM cells 131, a MRAM controller135 coupled to the MRAM cells 131, a RAID fail unit 133 coupled to aMRAM controller 135 and a data backup unit 134 coupled to the MRAMcontroller 135. MRAM cell 131 is the minimal unit in memory storage, andMRAM controller 135 controls the connection and operation of variousfunctional blocks in MRAM block 130.

Furthermore, a ReRAM block 140 is coupled a ReRAM RAID controller 108.The ReRAM block 140 includes multiple ReRAM cells 141, a hot spare 142coupled to the ReRAM cells 141, a ReRAM controller 144 coupled to theReRAM cells 141 and a RAID fail unit 143 coupled to the ReRAM controller144 and the hot spare 142. ReRAM cell 141 is the minimal unit in memorystorage, and ReRAM controller 144 controls the connection and operationof various functional blocks in ReRAM block 140.

In the embodiment of present invention, hybrid register 120 includes ahigh-speed data register 121, a middle-speed data register 122 and alow-speed data register 123. A data backup unit 102 is coupled to thehybrid register 120. The hybrid register 120 may be used to temporallystore instructions, data and addresses and to accelerate the executionof computer programs through rapid data access. In particular, to fitvarious memory architectures, three different registers 121, 122 and 123with high-speed/middle-speed/low-speed are used to temporally store thedata from memories with different read/write speeds. For example, thethree different speeds corresponds respectively to the cache 117 incomputing unit 110, the MRAM block 130 and the ReRAM block 140.

The computing unit 110 generally includes a chip 114, for example a chipto integrate system and peripheral components. A high-speed datacontroller 111, a middle-speed data controller 112 and a low-speed datacontroller 113 are coupled to the chip 114 to receive data withdifferent speeds from the hybrid register 120 or transfer correspondingdata thereto. A fiber channel 115 is coupled to the chip 114 to providehigh-speed internet connection. A processor 116, such as a command anddata processor, is coupled to the chip 114. The cache 117, such as astatic random access memory (SRAM), is coupled to the processor 116.

Please refer to FIG. 2 . In real implementation, the MRAM block 130 inthe embodiment may be used to replace conventional dynamic random accessmemory (DRAM) to act as a data buffer for the system, with the benefitof higher read/write speeds, non-volatility, high memory capacity anddensity. The ReRAM block 140 may be used to replace conventional flashmemory or solid state disks (SSD), which has lower read/write speeds,and act as a data storage device. The MRAM block 130 and the ReRAM block140 may be coupled to each other and be coupled to the cache 117, ex.SRAM, in the computing unit 110 through aforementioned common hybridregister 120. The computing unit 110 may process the data stored orbuffered in the three different memories.

After describing the system architecture of hybrid random access memoryof the present invention, FIGS. 3-14 will be referred in next embodimentto describe the process flow of manufacturing two different memories,i.e. MRAM and ReRAM, on the same substrate or wafer. Please notes that,since the components and features in regular front-end-of-line (FEOL)process is not the focus of the present invention, the description andillustration of the components in FEOL process, including gates,sources/drains, active areas or/and doped areas etc., will be omitted inthe embodiment and cross-sections. As a whole, the description of memoryprocess will begin from interlayer dielectrics and contacts in themiddle-end-of-line (MEOL) process.

Please refer to FIG. 3 . First, provide a substrate, such as a siliconsubstrate, with an interlayer dielectrics (ILD) 200 formed thereon. Inthe embodiment of present invention, a first region 201 and a secondregion 202 are demarcated on the substrate, wherein the first region 201is intended to form MRAM memory and the second region 202 is intended toform ReRAM memory. Other regions with different purposes, such as logicregion and peripheral region, may also be demarcated on the substrate,but they will not be shown in the figures.

In the embodiment of present invention, interlayer dielectrics 200 maybe a single layer structure or multilayer structure formed through CVDprocess with materials such as tetraethoxysilane (TEOS). Contacts CT areformed in the interlayer dielectrics 200 and are electrically connectedto gates, sources/drains and active areas (not shown) below formed inFEOL process. The material of contact CT may be Cu, Al W, etc., and abarrier layer (not shown) may be formed between contacts CT andinterlayer dielectrics 200. A thin dielectric capping layer 204 isformed on entire surface of the interlayer dielectrics 200. Contacts CTare also covered by the dielectric capping layer 204. The interlayerdielectrics 200 may act as a diffusion barrier and an etch stop layer,with materials such as silicon carbonitride (SiCN). In the embodiment,openings 205 will be formed in the dielectric capping layer 204 on thesecond region 202 to expose contacts CT below through photolithography.Opening will not be formed in the dielectric capping layer 204 on thefirst region 202 in this step.

Please refer to FIG. 4 . After openings 205 are formed, the bottomelectrode 208 of ReRAM cell is formed in the opening 205 to electricallyconnect the contact CT below. The material of bottom electrode 208 maybe tantalum nitride (TaN). The steps of forming bottom electrode 208 mayinclude: performing a CVD process to form a conformal bottom electrodematerial layer on the surface of dielectric capping layer 204,performing a CMP process with dielectric capping layer 204 as a stoplayer to remove the portion on the dielectric capping layer 204, so thatthe top surfaces of bottom electrode 208 and dielectric capping layer204 are flush.

Please refer to FIG. 5 . After bottom electrodes 208 are formed, atantalum oxide (TaO_(x)) layer 206, a tantalum pentaoxide (Ta₂O₅) layer209, an iridium layer 210, a ruthenium layer 212 and a titanium nitridelayer 214 are sequentially formed on the dielectric capping layer 204.In these layers, tantalum oxide layer 206, tantalum pentaoxide layer 209and iridium layer 210 may serve collectively as a variable resistiveportion of the ReRAM cell and may be formed through CVD or PVD process.The ruthenium layer 212 and titanium nitride layer 214 may servecollectively as a top electrode of the ReRAM cell and may be formedthrough PVD process, wherein the ruthenium layer 212 may also serve asan etch stop layer in the process.

Please refer to FIG. 6 . After the tantalum oxide layer 206, thetantalum pentaoxide layer 209, the iridium layer 210, the rutheniumlayer 212 and the titanium nitride layer 214 are formed, aphotolithography process is performed using the ruthenium layer 212 asan etch stop layer to pattern the titanium nitride layer 214, therebyforming the pattern of top electrode 216 of the ReRAM cell. In thisstep, the titanium nitride layer 214 on the first region 201 and thesecond region 202 are completely removed except the portion of patternedtop electrode 216 on the second region 202.

Please refer to FIG. 7 . After top electrodes 216 are formed, areactive-ion etching process is performed using top electrodes 216 as ahard mask and dielectric capping layer 204 as an etch stop layer toremove the tantalum oxide layer 206, the tantalum pentaoxide layer 209,the iridium layer 210 and the ruthenium layer 212 except the portionunder the top electrodes 216, thereby forming ReRAM cells with layerstructures such as the bottom electrode 208, a variable resistive layer(including tantalum oxide layer 206 and the tantalum pentaoxide layer209), the iridium layer 210 and the ruthenium layer 212. Afterwards, aconformal, protective capping layer 218 is formed on entire surface ofthe substrate. The capping layer 218 may be formed by CVD process usingmaterials such as silicon nitride.

Please refer to FIG. 8 . After the capping layer 218 are formed, ananisotropic etching process is performed to remove the capping layer 218on the surfaces of ReRAM cells and dielectric capping layer 204, so thatthe capping layer 218 only remains on sidewalls of the ReRAM cells andspacers 220 of the ReRAM cells are formed.

Please refer to FIG. 9 . After spacers 220 are formed, an inter-metaldielectrics (IMD) 224 is formed surrounding the ReRAM cells. Thematerial of inter-metal dielectrics 224 may be ultra low-k material suchas silicon oxycarbide (SiOC). The steps of forming inter-metaldielectrics 224 may include: performing a CVD process to deposit anultra low-k material layer on the surface of substrate, performing a CMPprocess with top electrodes 216 of the ReRAM cells as a stop layer toremove the portion above the top electrodes 216, so that the top surfaceof inter-metal dielectrics is flush with the top surface of topelectrode 216 of the ReRAM cell.

Refer still to FIG. 9 . After the inter-metal dielectrics 224 is formed,metal interconnects, such as first metal layer M1, may be formed in theinter-metal dielectrics 224 to electrically connect to the contacts CTbelow. The first metal layer M1 may be formed by single damasceneprocess using materials such as Cu, Co or Ru. Please note that in theembodiment of present invention, unlike ReRAM cells are formed only onthe second region 202 of the substrate, the first metal layer M1 may beformed on the first region 201 and the second region 202 of thesubstrate. Lastly, another thin dielectric capping layer 226 is formedon entire surface of the substrate to cover ReRAM cells and the firstmetal layer M1. Similarly, the material of interlayer dielectrics 226may be SiCN to serve as a diffusion barrier and an etch stop layer.

Please refer to FIG. 10 . After the dielectric capping layer 226 isformed, another inter-metal dielectrics 228 is formed on the dielectriccapping layer 226, and metal interconnects, such as vias V1 and a secondmetal layer M2, are formed in the inter-metal dielectrics 228, whereinvias V1 are electrically connected to the first metal layer M1 or thetop electrodes 216 of ReRAM cells below. The inter-metal dielectrics 228may be formed by CVD and CMP processes with a material such as ultralow-k dielectrics. Vias V1 and the second metal layer M2 may be formedby dual damascene process, which may include steps of etching theinter-metal dielectrics 228 with dielectric capping layer 226 as an stoplayer to form holes for the vias V1 and trenches for the second metallayer M2, then metal material such as Cu or Co is filled in the holesand trenches to form the metal interconnects. Lastly, another SiCN-baseddielectric capping layer 230 is formed on entire surface of thesubstrate to cover the second metal layer M2 and the inter-metaldielectrics 228.

After the manufacture of ReRAM cells (including the electricallyconnected interconnects such as vias V1 and second metal layer M2 above)are completed, RMAM cells will be manufactured on the level above theReRAM cells. This embodiment will illustrate the example of MRAM cellsmanufactured on a level next to the inter-metal dielectrics 228(including vias V2 and a third metal layer M3). Please note that theMRAM cells in the present invention may also be manufactured in otherinter-metal dielectrics level than the current one, and the MRAM cellswill only be formed on the first region 201, exclusive of the secondregion 202, so that they will not overlap the ReRAM cells on the secondregion 202.

Refer still to FIG. 10 . Firstly forming a dielectric layer 232 on thedielectric capping layer 230. The dielectric layer 232 may be formed byCVD process with a material such as TEOS, then vias 234 are formed inthe dielectric layer 232 on the first region 201. The material of vias234 is but not limited to W, Cu, Al, TiAl, CoWP or the group thereof.Vias 234 are electrically connected to the below interconnects, such asa second metal layer M2.

Please refer to FIG. 11 . After vias 234 are formed, a bottom electrodelayer 236, a magnetic tunnel junction (MTJ) layer 238 and a topelectrode layer 240 are formed sequentially on the dielectric layer 232.The bottom electrode layer 236, the magnetic tunnel junction layer 238and the top electrode layer 240 may be in-situ formed in the samechamber by PVD process. In the embodiment of present invention, thematerial of bottom electrode layer 236 is preferably conductive materialsuch as TaN, but is not limited thereto. In other embodiment of presentinvention, the bottom electrode layer 236 may include materials such asTa, Pt, Cu, Au, Al or the combination thereof. The magnetic tunneljunction layer 238 is a multilayer structure, which may include a seedlayer, a pinned layer, a reference layer, a tunnel barrier layer, a freelayer and a metal spacer.

In general, the pinned layer may be made of antiferromagnetic (AFM)materials, such as FeMn, PtMn, IrMn, NiO, etc., to fix or confine thedirection of magnetic moment of adjacent layers. The tunnel barrierlayer may be made of insulating oxide such as AlO_(x) or MgO, but notlimited thereto. The free layer is made of ferromagnetic materials, suchas Fe, Co, Ni or the alloys thereof (ex. CoFeB), but not limitedthereto. The direction of magnetization of the free layer will be freelychanged by external magnetic field. Since the structure of magnetictunnel junction layer 238 is not the focus of present invention, amagnetic tunnel junction layer 238 is used in the figure to representall of the above layer structures. The material of top electrode layer240 is preferably TiN.

Please refer to FIG. 12 . After the bottom electrode layer 236, themagnetic tunnel junction layer 238 and the top electrode layer 240 areformed, a photolithography process is performed to pattern the topelectrode layer 240, thereby forming the pattern of top electrodes 242of the MRAM cells. In this step, the top electrode layer 240 on thefirst region 201 and the second region 202 are completely removed exceptthe portion of patterned top electrode 242 on the first region 201.

Please refer to FIG. 13 . After the top electrodes 242 are formed, areactive-ion etching process is performed using the top electrodes 242as a hard mask to remove the magnetic tunnel junction layer 238 and thebottom electrode layer 236 except the portion under the top electrodes242, thereby forming MRAM cells with bottom electrodes 246, magnetictunnel junction layers 244 and top electrodes 242. Since thecharacteristics of ion beam etching process, the upper surface ofremaining dielectric layer 232 would be a concave surface slightly lowerthan the top surface of vias 234. Afterwards, a conformal, protectivecapping layer 252 is formed on entire surface of the substrate. Thecapping layer 252 may be formed by CVD process using materials such assilicon nitride. The material of the capping layer 252 may also includesilicon oxide, silicon oxynitride or silicon carbonitride, depending onthe requirement of the process.

Please refer to FIG. 14 . After the capping layer 252 is formed, aphotolithography process is performed to remove the capping layer 252and the dielectric layer 232 outside the MRAM region, thereby formingMRAM cells. After the MRAM cells are completed, an inter-metaldielectrics 248 surrounding the MRAM cells and interconnects such asvias V2 and third metal layer M3 inside the inter-metal dielectrics 248are formed, and a thin dielectric capping layer 250 is formed on entiresurface to cover the MRAM cells and the third metal layer M3. Thematerial and process of the components above is the same as the ones inaforementioned embodiment. Detailed description is no more repeated.

Please note that in other embodiment, the MRAM cells may be formed inhigher level rather than been limited in the level of via V2 and thirdmetal layer M3 as shown in the figure. In addition, other BEOL processesmay be followed up to form other components, such as upperinterconnects, top metal layer and bonding pads, in higher level afterthe MRAM cells are made. Since those processes and components are notthe focus of present invention, relevant description and figure areherein omitted.

In summary, the system architecture for hybrid random access memoryprovided in the present invention may integrate and use two differenttypes of RAM, i.e. ReRAM and MRAM, to meet the needs ofhigh-speed/low-speed access and digital/analog circuit. Moreover, thetwo different ReRAM and MRAM are manufactured on the same substrate orwafer in the same process flow, thus this system architecture issuitable for high-performance microcontroller, system-on-chip and AIapplication.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A hybrid random access memory in asystem-on-chip, comprising: a semiconductor substrate with amagnetoresistive random access memory (MRAM) region and a resistiverandom-access memory (ReRAM) region; a first dielectric layer on saidsemiconductor substrate, wherein said first dielectric layer is a firstinter-metal layer (IMD1); multiple ReRAM cells in said first dielectriclayer on said ReRAM region, wherein each of said ReRAM cells comprises:a first bottom electrode, wherein said first bottom electrode is formedin a dielectric capping layer under said first dielectric layer, and topsurfaces of said first bottom electrode and said dielectric cappinglayer are flush, and said first bottom electrode physically touches acontact below, and said contact is directly connected to an active areaof underlying said semiconductor substrate; a first top electrode abovesaid first bottom electrode; a variable resistive layer between saidfirst bottom electrode and said first top electrode; and spacers onsidewalls of said variable resistive layer and said first top electrode;a second dielectric layer above said first dielectric layer; andmultiple MRAM cells in said second dielectric layer on said MRAM region,wherein each of said MRAM cells comprises: a second bottom electrodeconnected directly to a via below, and said via is further connected toan underlying metal layer; a magnetic tunnel junction (MTJ) component onsaid second bottom electrode; a second top electrode on said magnetictunnel junction component; and a capping layer covering said second topelectrode and said magnetic tunnel junction component.
 2. The hybridrandom access memory in a system-on-chip according to claim 1, whereinsaid variable resistive layer is a multilayer structure with a tantalumoxide layer, a tantalum pentaoxide layer and an iridium layer.
 3. Thehybrid random access memory in a system-on-chip according to claim 1,wherein said first top electrode of each of said ReRAM cells isconnected to an overlying metal layer through a via.
 4. The hybridrandom access memory in a system-on-chip according to claim 1, whereinsaid magnetic tunnel junction component comprises a seed layer, a pinnedlayer, a reference layer, a tunnel barrier layer and a free layer.